1. Field of the Invention
The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, it relates to a semiconductor laser device comprising a semiconductor layer provided with a waveguide and a method of manufacturing the same.
2. Description of the Background Art
A nitride-based semiconductor laser device comprising a semiconductor layer provided with a striped waveguide is known in general, as disclosed in Japanese Patent Laying-Open No. 2003-17791, for example.
Referring to FIG. 29, a semiconductor layer 102 having a ridge portion 102a constituting a striped waveguide is formed on a GaN-based substrate 101 in the conventional nitride-based semiconductor laser device 1000 disclosed in the aforementioned Japanese Patent Laying-Open No. 2003-17791. This ridge portion 102a is provided at the center of the nitride-based semiconductor laser device in a cross direction (direction P). A p-side electrode 103 is provided on the semiconductor layer 102. An n-side electrode 104 in ohmic contact with the GaN-based substrate 101 is provided on a back surface of the GaN-based substrate 101. Two mirror facets 105 and 106 consisting of cleavage planes are formed to be orthogonal to the ridge portion 102a. These two mirror facets 105 and 106 constitute cavity facets.
Grooving portions 107 for cleavage introduction are formed on the GaN-based substrate 101, the semiconductor layer 102 and the p-side electrode 103. These grooving portions 107 are formed on the two mirror facets 105 and 106 consisting of the cleavage planes along a direction orthogonal to the ridge portion 102a at the same distance in the direction P leftwardly and rightwardly from the ridge portion 102a, to hold the ridge portion 102a provided at the center therebetween. In other words, the grooving portions 107 are horizontally symmetrically formed with respect to the ridge portion 102a. 
In this nitride-based semiconductor laser device, a metal wire 108 for supplying power to the p-side electrode 103 is wire-bonded to the p-side electrode 103.
In general, the metal wire 108 is usually wire-bonded to the center of the p-side electrode 103. Particularly when the length in the cross direction (direction P) is reduced due to downsizing of the nitride-based semiconductor laser device, the bonding position must be matched with the center, in order to increase allowance (margin) with respect to displacement in wire bonding.
In the structure of the nitride-based semiconductor laser device disclosed in the aforementioned Japanese Patent Laying-Open No. 2003-17791, however, the ridge portion 102a is formed at the center of the nitride-based semiconductor laser device, and hence the metal wire 108 is bonded to a portion immediately above the ridge portion 102a provided at the center when the metal wire 108 is bonded to the p-side electrode 103, if the length of the nitride-based semiconductor laser device in the cross direction (direction P) is reduced. Therefore, the ridge portion 102a (waveguide) is disadvantageously damaged in bonding of the metal wire 108 to deteriorate laser characteristics.
In the nitride-based semiconductor laser device, tensile stress is usually caused in an extensional direction of the waveguide and a direction orthogonal to this direction due to difference in lattice constants between a GaN layer and an AlGaN layer in forming the semiconductor layer. In the structure of the nitride-based semiconductor laser device disclosed in the aforementioned Japanese Patent Laying-Open No. 2003-17791, therefore, microcracks voluntarily caused between the grooving portions 107 in the form of broken lines formed on the semiconductor layer 102 may be formed in the cross direction (direction P in FIG. 29) of the semiconductor laser device while causing steps in the extensional direction of the waveguide (direction Q in FIG. 29) in the vicinity of the ridge portion 102a, when the wafer is cleaved in the form of a bar. In this case, the semiconductor layer 102 is cleaved starting from the microcracks having steps in the extensional direction (direction Q) of the waveguide, and hence the smooth cleavage planes (mirror facets 105 and 106) can not be obtained, and cleavage can not be excellently performed. Therefore, the ridge portion 102a (waveguide) is disadvantageously damaged.